1. Field of the Invention
The present invention relates to computer chassis for housing computer components, and more particularly, to portions of such chassis as relate to the insertion and removal of modular drawers.
2. Description of Related Art
Various forms of computer chassis are known in the art, for housing components of a computer system or networked computer systems. Such chassis are typically formed primarily of sheet metal components, such as formed sheet steel components, for strength and EMI shielding. In addition, computer chassis often include slots for sliding removable modular drawers into and out of the computer system. The removable drawers are themselves often housed in formed sheet metal housings. As is known in the art, sheet metal is an economical choice for electronics enclosures, but also entails compromises with respect to achievable tolerances and methods of assembly.
Customarily, computer chassis are provided with a plurality of slots, all of which are not necessarily occupied by a removable drawer when the computer system is in use. Often, a plurality of empty slots are available for the insertion of new drawers. A problem arises when drawers are not properly inserted. The first drawer may not be properly aligned in the slot, because of tolerances required to ensure ease of assembly. Consequently, sufficient space may not be left for drawers that will be subsequently inserted, and drawers may need to be removed and realigned to make room for the new drawers. This rearrangement of drawers wastes time, and increases the risk that the computer system will be disrupted by the rearrangement.
Also, if drawers are not properly aligned in their slots, electro-magnetic interference (“EMI”) gaskets may not be properly positioned. EMI gaskets may be a part of the drawer and/or chassis design to meet performance and regulatory requirements. If the drawers are not properly aligned to the system chassis, the assembled system may not meet its design specifications for control of EMI, resulting in an unacceptable amount of EMI emanating from the assembled system.
Prior-art computer chassis were not designed to solve these problems, which were not heretofore recognized as important. Although the presence of slots inherently involves a degree of guidance, prior-art chassis do not provide the necessary degree of precise guidance to avoid misalignment in a fool-proof fashion. Instead, prior-art systems rely on the skill of the assembler to properly align each drawer in the chassis, and to fasten each drawer in place after it has been aligned. Prior-art threaded fastenings are not desirable for providing precise alignment of each drawer, because of the difficulty of locating and threading fasteners into sheet-metal components in a precise way.
It is desirable, therefore, to provide a guide system for a computer chassis to ensure that new drawers are more precisely aligned in one of a plurality of empty slots, without the need for special attention by the person assembling the system. It is preferable that the guide system be independent of the fastening system for fastening the drawers to the chassis, and to require little or no additional cost of materials and assembly.